Shi No Kyodai
by ChallengerArrives
Summary: Rated T for Ichigo and Grimmjow. Challenge By ShiroHollow96. After the fight with the Quincy King, Ichigo and Grimmjow are sent to Katekyo Hitman Reborn dimension before season one, episode one.
1. Chapter 1

**Challenge given by: ShiroHollow96**

**Challenge: A Bleach and Katekyo Hitman Reborn. After the fight with the Quincy King, Ichigo and Grimmjow are sent to Katekyo Hitman Reborn dimension before season one, episode one.**

**Requirements: ****Ichigo has complete control of his hollow powers and has his duel zangetsu and can use all Quincy techniques and Kido and Shunko. Grimmjow can use Segunda Etapa and Shikai and Bankai and Kido. Pairings are cannon except Ichigo/Grimmjow, Ryohei/Yamamoto.**

**Optional:**

**My reaction upon finding the challenge: "." Uhm. I'll give it a shot.**

**This is a PM challenge, if you decide to take it, contact ShiroHollow96. I'm sure he'd be excited to read it.**

**Due to not actually ever finishing Bleach (Only got to meet Kitty... erm. *Cough cough* Shinji.) and a very confusing conversation where we talked about flames, kik, teenage paranoia, phones, Sailor Moon, NCIS, gender, and PMs coming in at the same time, we settled down with Hollow powers for Ichigo and Shikai/Bankai for Grimmjow for now. Until I get more information.**

* * *

**Chapter 1 To Namimori**

All Ichigo remembered was a fighting the Quincy king and the next thing he knew, he was having a hazy chat with the Soul King along with Grimmjow and two other people. A flash of white light and rainbows. Then pain, a whole lot of it.

He felt like he was being boiled, his bones felt like they were shrinking. Well, pain was something he was used to. He heard screaming, he didn't know if it was his. There seemed to be more than one.

When he woke, the first thing he saw was white. A LOT of white. Urgh, hospitals. He really preferred his family clinic.

Ichigo rolled over in an attempt to get out of the bed and find out what was going on. Emphasis on_ attempt._

His vision was covered by light blue. His nose and mouth were covered by cat hair. He jerked back.

A panther cub. A light blue panther cub.

Ichigo only knew of one cat with that colored hair. "Gr-Grimmjow?" he asked uncertainly.

The cub groggily opened an eye to look at him grumpily. "What?" it asked.

The cub that was apparently Grimmjow had a high-pitched voice comparable to that of a five-year old girl.

Ichigo stared in shock for a moment as his mind caught up, once it did, he burst out laughing like there was no tomorrow, tears gathering at the edges of his eyes. He clutched his sides in the pain of laughing too much.

Right up to the point Grimmjow bit his leg. To which the carrot headed shinigami yelped in pain.

"You're going to pay for that!" Ichigo yelled as he lunged at the cub, who merely jumped out of the way.

"Not while you're in that state, brat."

"What the hell are you talking about! I'm completely fine! And who're you callin' a brat!"

Grimmjow hummed. "Notice anything different?"

Ichigo looked around. Now that he pointed it out, everything was a lot bigger than he was used to.

...

?

Ichigo looked into the (badly placed) mirror behind the bed. What he saw was a child looking back at him. A seven year old orange haired child.

...

"What. The. Fuck?!" he bit out.

Grimmjow laughed. "Least I'm not a kid."

"I think I'm better off as a kid than a blue panther cub with the voice of a female toddler." Ichigo retorted.

"What are _you_ going on about?!" Grimmjow growled out.

"You clearly haven't seen a mirror." Ichigo said with a grin. He picked up Grimmjow, who struggled in his grasp, and brought him up to a mirror. Grimmjow stopped struggling and stared in horror.

"MMMMRRRRRYYYYAAAAAAOOOWWWWW!"

It seems that the noise they made finally caused someone to check up on them.

A nurse came and she screamed. "PUT THAT THING DOWN!"

"What'd you just call me?! You did not just call me a thing! Let me go, Kurosaki, I need to rip her apart!"

Ichigo froze. Talking panther cub. (Probably) Normal woman. Not a good mix.

Luckily it seemed she couldn't understand him. It must be only the ones with high spiritual energy who could understand the animal changed people... arrancar... things... come to think of it, what category did they fall under?

A sigh of relief escaped Ichigo and he held onto Grimmjow tighter. He muttered an order for the cub to calm down. Not that Grimmjow listened. He glared at the woman and continued hissing. At least he stopped struggling.

Ichigo wondered...

He scratched the back of Grimmjow's ear. The light blue kitten melted and began purring.

The woman seemed to snap out of her stupor. "P-put it down, b-boy." she said.

"No." Ichigo said. Making sure he seemed like a stubborn child. No one would believe it if he said he was really a high school teen, after all. At worst, he'd be thrown in a mental hospital and at best, they'd think that it was nothing but a child's rambling of an imaginary world. Until he left the hospital, he'd pretend to be a child. After all, knowing him, he'd be unable to keep up that rouse for long.

"Kid, that thing is dangerous." a doctor said from behind the nurse.

He scratched the underside of the cub's chin. "Jaquez won't hurt anyone who doesn't annoy him."

Grimmjow gave Ichigo an irritated look that was soon forgotten in favor of the scratching.

Ichigo snickered. If only he'd known this about Grimmjow during while they went to save Orihime.

* * *

"What's your name, kid." asked a different doctor who was eyeing Grimmjow warily. Grimmjow, however, was sulking.

"Ichigo." he replied shortly.

"How old are you," he asked.

"Don't know." Ichigo replied.

The interrogation continued with Ichigo answering the majority of the questions with don't know. It would have to do until he had a chance to talk to Grimmjow about what the soul king had said. He vaguely recalled something about different worlds...

* * *

A week later and Ichigo and Grimmjow were left at an orphanage. One they left as soon as night fell. Ichigo felt a bit bad about that but there was no way he was staying at an orphanage, they'd forget him soon anyway.

Now, a month later, Ichigo and Grimmjow were wandering the around the Japan so like their own but not.

They had made sense that the world was a different one and that the Soul King had sent them there for some reason, but neither remembered why.

Ichigo was unsure of why Grimmjow hadn't left but grateful for the familiar company.

Sort of.

The two fell into a familiar banter as they reached a town called Namimori.

* * *

They walked around the town of Namimori, both dirty and slightly hungry. Both were used to it so it didn't bother either of them. As it turned out, when there wasn't much to worry about, Ichigo could be very manipulative.

He played an innocent child with a pet cat that had been kicked out of an orphanage because someone had been allergic to cats. Oddly enough, no one realized that Grimmjow was a panther not a cat. No one even commented on his odd coloring.

When Grimmjow pointed this out, Ichigo shrugged. "Most Japanese don't care for oddities like that, it's the human physical oddities that get to them. Not anything like disorders but more like hair and eye colors. Things like spiritual energy are brushed off for the most part. We're just like that."

"Weird humans." had been the feline's reply.

Ichigo would clean the dishes and some rooms and slip away with Grimmjow during the night.

Neither of them knew, but it had been on the news. If a strange orphan with an odd cat approaches your house, take them in, you'll get good luck. However, if you do it with the thought of greedily getting luck, bad things will befall.

* * *

Not an hour of walking around Namimori and Ichigo had seen a kid being bullied.

An image of the same thing happening to Yuzu had Ichigo taking down the bullies without a second thought.

When Ichigo got a better view of the kid, he realized it was a boy, one two years younger than his physical age. "Oi, kid, you okay?"

"Tsu-kun is fine." the apparent 'Tsu-kun' said with tears in his eyes.

"You're getting soft, Kurosaki." Grimmjow stated.

"Hiee! The cat talks!" Tsu-kun yelped. Ichigo blinked in surprise.

Grimmjow looked at the kid in a new light. "Brat, you can understand me? Heh, that's interesting. What's your name?"

"Sawada Tsunayoshi!" he yelped again.

* * *

**If I got anything wrong on the Bleach side, I haven't watched Bleach in a LONG time. If I got anything wrong on the KHR side, send someone to make sure I haven't committed suicide.**

**1,610 I know it's super short, but someone is impatient.**

**S****hiroHollow96, I hope you don't mind. I'm pretty sure KHR and Bleach don't really have pairings, so I'll BS them a bit. As for the other two, you know who one is but can you guess the other?**

**To the readers, I'll post the next chapter when one of you guess who the two are. Good Luck~. (Minimum time is one month. I still have my life and other stories, after all.)**

**HINT: Orange flowers and hair down the center of face**


	2. Chapter 2 Moving In

**Next chapter is finally up! That doesn't mean you get to know who those people were. But two people got it right. One was the person who requested and the other was... telling you would give it away.**

**KingYohannE - Right now.**

**C.S.Y. Shadows - Congrats on getting the right answer!**

**Hibarilova18 - First, love the name. Second, 18 is awesome. Third, 18 is will always be the coolest. Fourth, thanks for the review. ;P**

**Bl4ze777 - How many times do you win at slot machines? Sorry, I couldn't resist. Yes, I do realize my sense of humor sucks. Thanks for the review and I hope I didn't offend you somehow.**

* * *

**Chapter 2 Moving in**

It didn't take long for Ichigo and Grimmjow to take a liking to the little, helpless brunette. At least, not for Ichigo. After all, Tsuna was still in awe over the talking blue feline.

However, it did seem that Grimmjow had taken pleasure in scaring the brunette, which led to said brunette running to Ichigo for help, leading to a fight between Ichigo and Grimmjow. Never once did they fail to fight in a flashy and spectacular fashion that somehow didn't blow up the entire country.

Ichigo suspected two things.

One, Japan and its civilians - no matter what world - were made out of some strange substance that was highly resistant to destruction by... scratch that. Highly resistant to mass destruction in general and could rebuild itself overnight. And said mass destruction happened often. It would certainly explain a lot. Like how no bat an eyelash at a kid fighting a panther cub, and blown up parks that somehow fixed themselves overnight. Of course, everything had a limit, which was why people still died by mundane things. Or maybe it was something that activated only during times of mass destruction. Either way worked.

Two, Grimmjow and Tsuna were doing this on purpose. Grimmjow wanted a fight with a bonus of scaring a rabbit-like brunette and Tsuna liked watching them and cheering them on. The first one was very plausible, but the second one had developed after the twenty second fight. Tsuna had freaked out during the first ten, gotten used to them by the fifteenth, and was quite comfortable causing them by the thirtieth one... In one month.

He was sure of one thing.

These two were going to drive him insane.

* * *

Grimmjow found he could return to his humanoid form. He just hadn't figured out how to do it completely so he stuck to staying as a cub for the most part.

The first time he had successfully changed back had been humiliating.

Tsuna had flipped out. First, the feline could talk, now he could turn into a person?!

Ichigo laughed harder than he had in his entire laugh when he realized Grimmjow had kept his tail, ears, whiskers, and paws. This, of course, led to another fight, in which Grimmjow put his claws to good use, that destroyed a mountain. And of course, it being in Japan, the damn thing was back by the next day.

It had been a huge WTF?! moment for both Ichigo and Tsuna. Grimmjow didn't see anything wrong with it. In the end, they chalked it up to the mysteries of Japan and ignored everything of that sort that came after.

...

...

...

For the most part.

* * *

All the fighting had caught the attention of a certain demon of Namimori.

It had started out like any other day. With Tsuna running to Ichigo to stop Grimmjow from chasing him and a fight broke out at the park. At this point, Grimmjow only had ears and a tail that could easily be hidden away. Midway, there had been an interruption.

"Herbivores. You have destroyed Namimori property, prepared to be bitten to death!"

"Hieee! It's Hibari!"

"...Bitten to death?" asked Ichigo.

"Oi, kid, you're perfectly fine watching us fight but you're afraid of him?" Grimmjow asked.

"'Cause Tsu-kun know you aren't going to hit Tsu-kun when you two are fighting." he replied simply, hiding behind Ichigo.

Luckily for Tsuna, Hibari attack Grimmjow first.

However, Grimmjow dodged each and every one of the attacks. Occasionally, Grimmjow threw in an attack but he was mostly fooling around.

"Ne. Ichi-nii, how long do you think this is going to take?"

"Until Grimmjow decides to stop messing around probably. He's pretty good, but he... damn, I can't say anything about it without being a hypocrite. Uh, let's just say he doesn't have enough experience."

"...In other words, a long time?"

"I'd give it about five to ten minutes."

* * *

In actuality, it took three minutes for Grimmjow to get bored and pass Hibari to Ichigo.

Ichigo had to admit, the kid was good. He was fast - not shunpo fast but fast for a six year old - and light on his feet, his hits were on par with the average person twice his age. But, he was full of openings and...

Ichigo made a sudden swerved to his left.

Hibari tripped and fell over.

His balance sucked and usually the kid ran in a straight line.

The black haired male glared at him.

It wasn't as scary as it was cute. And Ichigo said so.

The glare turned into a scowl.

"You should really work on your balance." Ichigo offered. "Cover your left side more but don't neglect the right side. And don't make so many unnecessary movements. You'll tire out faster and give more openings. Bye!" He grabbed Tsuna and hightailed out of the park with Hibari chasing after him.

"Oi! Grimmjow, hurry up."

"What? You're running from this brat?"

* * *

Grimmjow, as a panther cub, stared an Tsuna.

Tsuna gripped Ichigo's sleeve in fear.

"Grimmjow, stop scaring him." Honestly, it felt like he was looking after pre-schoolers... well with their physical ages it wasn't all that far off.

"Ichigo, we need to teach this brat how to fight."

"Hah?"

"He's weak and his confidence is annoyingly low. He's a coward."

"Grimmjow, he's five."

"So what?"

"He's just a kid! He shouldn't be fighting!"

"What about that lieutenant girl, Yachi whatsit."

"Yachiru, and she's different!"

"Or that little captain with the white hair."

"Toushiro?"

"Yeah, him."

"Yachiru and Toushiro are part of the Gotei 13 and technically, neither of them are kids."

"That kid from yesterday?"

"..."

"I'm not saying we should make him a fighter, just build some confidence and the ability to defend himself. Although, turning this kid into fighter would be..."

"Tsuna, what do you think?" Ichigo asked leaving Grimmjow to his musings

"Tsu-kun doesn't want to hurt anybody."

"Not to hurt, to protect yourself and others."

"Like you?"

"Uh, sure?"

"Okay." That was easy.

* * *

**So chapter two is up and everyone seems out of character. 'Specially Grimmjow.**

**Care to tell me what you think?**


	3. Chapter 3

**Geez, I am insane. An update for every fic, forget that I just finished writing one for this one. I was going to give full chapters, but I ran out of time. Late Merry Christmas to everyone.**

**Bl4ze777 - How often do you win at Slots? . I'm sorry, I couldn't help it! So what joke were you talking about? = Dude, I still don't know what joke you're talking about.**

* * *

**Chapter 3**

Tsuna's training was slow and complex. It was a given as neither Ichigo or Grimmjow had actual proper training. Well, Ichigo had learned the basics in a dojo once, but all that had turned into instinct after his mother's death. He didn't really remember much. So they started with Tsuna's endurance.

One lap around the block. Five push ups. Five sit ups. Five crunches.

Simple things like that. You couldn't really push a five year old that much.

When the skylark had found out what they were up to, he decided to pitch in. Ichigo and Grimmjow allowed him to take over since the kid seemed to have a better idea than they did. They just made sure that Hibari didn't go overboard and occasionally gave advice when things got practical.

Then came a baby in a red Chinese tangzhuang with a pet monkey.

Ichigo tried to wrap his head around the idea that the baby, that was about one year old, was Hibari's uncle and could speak fluently in both Chinese and Japanese. He failed... miserably. Especially after learning the baby was a master of 107 martial arts styles.

Tsuna's mind had blown a fuse.

Grimmjow, in his humanoid form, shook himself out his stupor and challenged the credibility only to end up in a crumpled heap on the ground with no mobility in any of his limbs before he could even get into a fighting stance. That was a blow to his pride. A really, really big blow. He sulked in cat form for weeks while Tsuna trained under the toddler.

Ichigo was really disturbed by the toddler. He spoke, acted, and fought like an adult who had trained since birth. His spirit energy -according to Grimmjow- was pretty high as well. Most of all, he acted like Grimmjow's cat form was completely normal _after_ he started talking.

Ichigo was sure nothing could sway Fon's - the very adult-like toddler - from his ridiculously calm demeanor and when he mentioned it to Grimmjow, the blue panther seemed to take it as a challenge to break the said unflappable adult-ish toddler...child...person... what exactly do you call someone like Fon?

'I wonder if he's an alien.' Ichigo thought before shaking the thought out of his mind. He was clearly spending too much time with the nonsensical portion of Japan. Shinigami were believable. Dimension travel was believable. Grimmjow as a cat was believable.

But aliens? Hell no, he needed _some _semi-balance of reality after all. What was next? Shape-shifting lizards?

A shiver ran down his spine. 'Why do I feel like I just jinxed myself?' he wondered.

Miles away, a lizard sitting on a fedora sneezed.

* * *

Three years after Tsuna started training under Fon, they had discovered a new side to the eight year old.

He was a prankster.

That had been unexpected. (Not really, in hindsight.)

If Tsuna respected someone, he would either a prank them to oblivion (or at least attempt to) or b) not prank them at all. If he didn't have any respect for someone, he would prank them to hell. (Yes, there is a difference.)

Grimmjow had learned Tsuna was a ruthless prankster when he woke up in his cat form wearing a princess dress - tiara included - and covered in glitter.

Needless to say, Ichigo enjoyed each and every prank Tsuna played. Especially since he was never got caught by any of the pranks.

"The little brat," Grimmjow growled. "I swear, I'll-"

"You'll what?" Ichigo asked with amusement. "You haven't ever actually harmed him much."

"Why do we stay here?" Grimmjow groaned.

"Entertainment." Ichigo replied. "And Nana's a pretty good cook. What I want to know is why you let the kid prank you so often and let him get away with it."

Grimmjow grumbled under his breath.

"Well, it helps with his stealth anyway." Ichigo laughed.

"You seem different."

"I have nothing to do, so much stress has been taken off my shoulders. I've forgotten what it's like to relax and just be a kid. "

Grimmjow had to agree, as much as he liked fighting the opportunity to just relax was nice.

...

"I'm bored." Grimmjow said. And with that, he attacked Ichigo, forgetting he was in his cat form.

* * *

Tsuna was walking in the park when he noticed Yamamoto Takeshi staring at people with a sad look in his eyes.

"Ah, Yamamoto-san, are you okay?" asked Tsuna.

Yamamoto smiled. "Of course I am! Why wouldn't I be?"

Tsuna swore there were sparkles behind him but that smile... "That smile looks so fake." he deadpanned.

"...eh? What are you talking about?"

Tsuna sighed. "Well, if you need someone to listen to your troubles, I'll be waiting." He left Yamamoto standing in the park with a dumbfounded look on his face.

'Wow, Tsuna turned out pretty cold. This is our fault isn't it?' Ichigo thought with a sweatdrop. "Ah, Tsuna, does he even know your name?" he whispered.

Tsuna froze. "I didn't tell him! Shoot, what do I do?! It'd look lame if I go back just to tell him." he hissed back.

Grimmjow looked down at Tsuna from his seat on Ichigo's shoulders. "How'd you know his name?"

"We go to the same school." Tsuna said.

"Then why are you worried 'bout it?"

"Hehe, I forgot for a second."

"Baka Gaki."

"Who're you calling a stupid brat!"

* * *

**I am tempted to make this a crack fic, but I won't since I'm not good at them.**

**This story is slowly progressing...**


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